1. Field of the Invention
The present invention relates to a method of identifying a type of optical disc, and more particularly, to a method of identifying an optical disc as a single-layer disc or a dual-layer disc, in which levels of high-frequency signals reflected from the optical disc are compared with reference values set according to characteristics of the optical disc.
2. Description of the Related Art
In general, an optical recording medium such as a compact disc (CD) or digital versatile disc (DVD) has a diameter of several inches and a thickness of 1.2 mm, has a reflective surface as a data recording layer, and stores information such as sound, text, and graphics in the form of combinations of pits on the reflective surface. An optical recording medium has a capacity to store more data than a conventional floppy disc, which is a magnetic recording medium that may store roughly 2 megabytes of data. An apparatus to reproduce data recorded on an optical disc at ultrahigh-density at a high speed without any error in reading, has been developed with the development of ultrahigh-density optical discs. An apparatus to reproduce data recorded on various types of optical discs has been developed so that a user is not confined to use of a single type of optical disc.
In general, optical discs include CDs and DVDs, and DVDs include DVD-Ss and DVD-Ds. CDs include CDs for audio data and CDs for video and audio data. DVDs include DVD-Ss in which only one set of data is recorded in a track as a single layer, and DVD-Ds in which two sets of data are recorded in a track as a dual layer.
Conventionally, to distinguish between a single-layer disc and a dual-layer disc, an optical disc is identified as a dual-layer disc when predetermined (fixed) reference values are compared with and determined to be larger than levels of predetermined first and second high-frequency signals which are reflected from the disc. An optical disc is identified as a single-layer disc when predetermined (fixed) reference values are compared with and determined to be smaller than the levels of the predetermined first and second high-frequency signals which are reflected from the disc.
However, a reflection factor of the predetermined levels of the first and second high-frequency signals is lowered according to a difference in sensitivity of a pickup, which operates during reproducing data from an optical disc. As a result, it is difficult to accurately identify a type of optical disc, and thus it is difficult to smoothly reproduce data from the optical disc.